1. Technical Field
The present invention relates to a display device, and more particularly to a display device such as a liquid crystal display.
2. Related Art
As a related-art display device, a liquid crystal display which uses changes of the optical property of liquid crystal for displaying characters and/or images is known. Related-art liquid crystal displays include a vertical-electric-field-mode or lateral-electric-field-mode liquid crystal display.
Generally, related-art liquid crystal displays include a liquid crystal display panel having a structure in which a TFT and a CF substrates are placed facing each other and sandwiching a liquid crystal layer therebetween. The TFT substrate is a substrate onto which a thin-film transistor (TFT) is built on the surface thereof facing the CF substrate. The CF substrate is a substrate on which a color filter (CF) is formed on the surface thereof facing the TFT substrate. In a related-art vertical-electric-field-mode liquid crystal display, an electrode is formed each on the surface, facing the CF substrate, of the TFT substrate and on the surface, facing the TFT substrate, of the CF substrate, and the vertical electric field generated by the electrodes controls the alignment of liquid crystal molecules within the liquid crystal layer. In a related-art lateral-electric-field-mode liquid crystal display, an electrode is formed only on the surface, facing the CF substrate, of the TFT substrate, and the lateral electric field generated by the electrode controls the alignment of liquid crystal molecules within the liquid crystal layer. In the ways described above, in the related-art liquid crystal display, various characters and images are displayed by changing the optical transmittance by controlling the alignment of liquid crystal molecules within the liquid crystal layer.
It should be noted that in the aforementioned related-art lateral-electric-field-mode liquid crystal display, there is a disadvantage that an unintended electric field is applied to the liquid crystal layer because of the generation of static electricity on one of the surfaces of the liquid crystal display panel (more specifically, on the side of the CF substrate on which an electrode is not formed). Thus, in the related-art lateral-electric-field-mode liquid crystal display, static protection is adapted to be provided on one of the surfaces of the liquid crystal display panel (more specifically, on the side of the CF substrate on which an electrode is not formed). (See, for example, JP-A-9-258203.)
JP-A-9-258203 discloses a lateral-electric-field-mode liquid crystal display wherein a transparent conductive film is disposed on the surface, opposite from the TFT substrate, of the CF substrate and the transparent conductive film is electrically connected to a metal case for storing a liquid crystal display panel. In JP-A-9-258203, static protection on one of the surfaces of the liquid crystal display panel (more specifically, on the side of the CF substrate on which an electrode is not formed) is provided by connecting a metal case to the ground potential. However, no specific method of how the metal case should be connected to the ground potential is described.
The aforementioned related-art lateral-electric-field-mode liquid crystal display is sometimes used for a head-up display mounted on a vehicle and the like. Generally in those cases, there is not an enough space available for static protection because the lateral-electric-field-mode liquid crystal display used in those cases is small, with the result that there is a disadvantage that it is difficult to provide static protection on one of the surfaces of the liquid crystal display (more specifically, on the side of the CF substrate on which an electrode is not formed) when a liquid crystal display panel used as a car mounted head-up display is small.